With conventional electronically controlled automatic transmissions for vehicles, the speed change timing for speed change control is generally preset in the following manner.
The automatic transmission is provided with a map of speed change patterns in which speed change positions (gear positions) are set so as to give an optimum torque to suit the vehicle speed and throttle valve opening. Speed change control is carried out on the basis of this map when the select lever is in the D-range (drive range) position (see for example unexamined Japanese utility model publication No. 62-194231).
With the conventional arrangement however, wherein the speed change position is read from a map of set speed change positions versus vehicle speed and throttle valve opening, and set to a speed change position based on the current vehicle speed and throttle valve opening, the control characteristic target for the speed change timing is preset. Hence in the case of a vehicle traveling topography environment, with changes in altitude for example, then due to the reduction in air density at high altitudes, a discrepancy occurs in the relationship between throttle valve opening and engine torque at higher or lower altitudes. With the conventional arrangement, the engine torque is lower at the higher altitude compared to that at a lower altitude for the same throttle valve opening.
Further, with increased running resistance when driving up hill, the preset speed change map no longer conforms to the optimum speed change pattern. The driver thus experiences a different drive feel, and throttle control and selector control become troublesome.
It is also difficult with the conventional arrangement to obtain a speed change control with caters equally to the individual needs of a large variety of drivers.
In view of the foregoing, it is an object of the present invention to provide a speed change controller whereby speed change timing can be controlled appropriately to suit environmental changes, and which can cater equally to the individual needs of a large variety of drivers, by means of a novel structure realized by the present inventors wherein a speed change curve is determined by limting a speed change region.